Baltimore County police said they've charged a man already accused in the 14-year-old killing of his former girlfriend of also trying to intimidate a witness in the case.

Police in March charged Stephen Cooke Jr., 43, of Pasadena, with first-degree murder. They said he hired someone to kill his girlfriend, 24-year-old Heidi Bernadzikowski, in her Codd Avenue home in Dundalk in 2000.

This week, officials decided to also charge him with witness intimidation in connection with his trial.

Detectives said they believed almost from the start that Cooke conspired to kill Bernadzikowski, but they had never been able to prove his involvement until another man, Alexander Bennett, was arrested in January 2012 after police said they discovered DNA evidence linking him to the crime.

Police said Bennett, 34, of Greeley, Colorado, identified Cooke as the person behind the killing.

Investigators said they believe Cooke hired Bennett and another man, Grant Lewis, 35, of Denver, Colorado, through the Internet to kill Bernadzikowski because he wanted to collect a $700,000 insurance policy he purchased on her.

Lewis was the middle man and stayed in Colorado, while Bennett came to Maryland, strangling and cutting Bernadzikowski's throat, according to police.

Bennett was charged with first-degree murder in the case. Lewis was charged with conspiracy to commit murder. Both are still in jail awaiting trial.

Investigators said they later discovered that Cooke tried to hire another inmate at the Baltimore County Detention Center to hurt Lewis so he couldn't testify against him.

Cooke has now additionally been charged with conspiracy to commit witness intimidation and conspiracy to commit first-degree murder. He continues to be held without bail on all charges.